MAGNETOSENSITIVITY IN LIVING-BEINGS

The presence of a continuous magnetic field is one of the components o f the terrestrial environment in which living species have differentia ted and have evolved since the origins of life. The list of species li kely to modify their behaviour under the influence of this magnetic fi eld extends from bacteria to vertebrates. The mechanisms responsible f or the sensitivity to the terrestrial magnetic field appear as varied as the number of known specific cases. The most simple explanation is the presence of intracellular inclusions in bacteria (magnetite crysta ls or magnetosomes, generally arranged in chains). More elaborate syst ems, involving the nervous system (peripheral and central) are suggest ed to exist in vertebrates. Apart from the case of certain teleost fis h, where magnetosensitivity results from the use of systemps allowing the perception of magnetic fields, most of the other mechanisms appear to be based on the existence of magnetite crystals. The relation betw een these crystals and the peripheral nerves, but above all the centra l nervous system, still remains unclear. The perception by superior ve rtebrates, including man, of alternative magnetic fields ov very low f requency, which are added to the terrestrial field, remains the object of debate. Their possible impact on health has been extensively studi ed in the last ten years.